She should play Harley Quinn
I don't know if they're ever going to include the Joker's sidekick/love interest/pain in the a$s Harley Quinn in the movie series, but I think Lori Petty would be perfect. She can do the squeaky voice and working-class accent without sounding like a bimbo, she can do comedy and drama and she's got the right physique. I say put her in red and black and let 'er rip.
However, she's probably too old at this point, and if they do cast Harley, they'll probably want somebody with more star power.